Progressive Retinal Atrophy (PRA)

PRA affects the entire retina and is the canine equivalent of retinitis pigmentosa. This disease manifests itself differently in different breeds. The most common form of PRA in the collie is detectable at early age (6wks and over). The form of PRA in Irish Setters is also early-onset. In Labrador Retrievers, on the other hand, the age of onset is much later, typically four to six years of age, making it much harder to find and isolate carriers in this breed.

PRA has been detected as early as six weeks in puppies in some breeds, such puppies are usually blind by six to eight months. An electroretinography can be used to detect the early signs of PRA. Animals to be tested in this manner are anesthetized while lenses are placed on the eyes to record the retina's reaction to light. (Like wearing contacts.) In other cases, ophthalmological examination by ACVO-certified vets can pick up cases of PRA and confirm them with electroretinography if desired.

All dogs affected with PRA eventually become blind. Carriers show no clinical symptoms. Symptoms are subtle, starting with night blindness, some eye dilation, to progressive blindness. It's quite common to not notice anything is wrong until the dog is nearly completely blind. Proactive testing is always recommended, especially dogs being used for breeding.

Current research is beginning to isolate the genetic markers for this disease. At present, there is a genetic test to identify carrier and affected dogs for the Labrador Retriever. This disease is thought to be a simple autosomal recessive gene. Thus two recessive genes are needed for a dog to be affected. A single recessive gene masked by the healthy dominant means the dog is a carrier. Therefore, an affected dog's parents are carriers or also affected.

PRA Disease

The genetic disorder, prcd-PRA , causes cells in the retina at the back of the eye to degenerate and die, even though the cells seem to  develop normally early in life. The “rod” cells operate in low light levels and are the first to lose normal function. Night blindness results. Then the “cone” cells gradually lose their normal function in full light situations. Most affected dogs will eventually be blind. Typically, the clinical disease is recognized first in early adolescence or early adulthood. Since age at onset of disease varies among breeds, you should read specific information for your dog. Diagnosis of retinal disease can be difficult. Conditions that seem to be prcd-PRA might instead be another disease and might not be inherited. It’s important to remember that not all retinal disease is PRA and not all PRA is the prcd form of PRA. Annual eye exams by a veterinary ophthalmologist will build a history of eye health that will help to diagnose disease.

Unfortunately, at this time there is no treatment or cure for PRA. If your dog is affected, you may find it helpful to read about other owners’ experiences living with blind dogs. (suggested links:www.eyevet.org and www.blinddogs.com)

NOTE: In October 1945 the Kennel Club of England added PRA to the list of disqualifications from winning any award in the show ring.